Fossil flies in Baltic amber - insights in the diversity of Tertiary Acalyptratae (Diptera, Schizophora), with new morphological characters and a key based on 1,000 collected inclusions

2009·1.2 MB·English

by  Von Tschirnhaus, Michael

© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
Fossil flies in Baltic amber –
insights in the diversity of Tertiary Acalyptratae
(Diptera, Schizophora),
with new morphological characters and a key based
on 1,000 collected inclusions
Michael VON TSCHIRNHAUS & Christel HOFFEINS
Abstract: A review of specific publications dealing with Baltic amber Diptera, Acalyptratae, from the years 1822 until 2008 in-
cludes 38 articles. H. LOEWwas the first entomologist searching systematically for Diptera in amber. Two of his three articles are
discussed. Parts of his first one (1850) are translated from German because of its extreme rarity in libraries. From Eocene Baltic
amber 35 families of acalyptrates are known now, a further four from British Eocene sediments. Natalimyzidae, ?Piophilidae and
Pyrgotidae are recorded for the first time, Natalimyzawas known only from the recent Afrotropical fauna. Different counts of the
percentage of acalyptrates among insect-, Diptera- and “true fly“-inclusions, respectively, are compared. Less than 1% of all flies
belong here. Reasons for this rarity are discussed together with an overview of the rare aggregation of acalyptrates in single am-
ber pieces. Peculiar morphological apomorphies, which enable family identification worldwide because of their singularity, were
already present during the Tertiary. Three such examples are discussed. The dispute about the doubted synchroneous genesis of
German Bitterfeld amber is solved by demonstrating 15 conspecific acalyptrate species in both deposits. Intraspecific variability
of an amber acalyptrate has never been studied before. On the basis of 45 specimens and the holotype of Protoscinella electrica
(Chloropidae) the slowness of evolutionary transformations is exemplified with the background of the phylogenetic value of 16
selected characters. A spotlight is thrown on the polyphyletic reduction process in wing venation and bristle equipment observed
in several families of acalyptrates.
The systematic part presents overviews of a large number of morphological details used for taxonomy. Two tables enable the easy
check and documentation of each detected specimen, as well as an understanding of the puzzling termini and abbreviation sys-
tems in subsequent periods of dipterology. Two differently organized identification keys are presented: one listing 97 exceptional,
rare, or newly detected morphological pecularities, a second one is a trial to key out all 56 described and all 161 detected unde-
scribed species. The well known terminology of HENNIG‘s publication series on amber is used in order to enable an easy cross-ref-
erence to his partly complicated descriptions, to his plentity of figures, and to the dipterous literature until the year 1981 when a
new terminology was proposed. All family- and generic transfers since HENNIG‘s times are listed with their references, as well a
species breakdown of parts of the identified 1,141 inclusions.
Key words: Apomorphies, Bitterfeld amber, Calyptratae, chaetotaxy, Chloropidae, Pyrgotidae, speciation, variability.
.
Santrauka: 1822-2008 metais paskelbtos 38 mokslines publikacijos, skirtos Baltijos gintare rastiems Diptera, Acalyptratae
.
vabzdžiams. H. LOEWASbuvo pirmasis entomologas, sistematiškai tyrineje˛s dvisparnius gintare. Aptariami du iš triju˛ jo straipsniu˛.
Atskiros jo pirmojo darbo (1850) dalys yra išverstos iš vokiecˇiu˛ kalbos, nes publikacija yra tapusi didele bibliografine retenybe. Iš
.
eoceninio Baltijos gintaro dabartiniu metu žinomos 35 akaliptratiniu˛ dvisparniu˛ (Acalyptratae) šeimos. Dar trys rastos eoceninese
nuogulose Didžiojoje Britanijos. Agromyzidae, Natalimyzidae, Piophilidae, Pyrgotidae ir Sphaeroceridae yra aprašomos pirma˛ kar-
.
ta˛, Natalimyzabuvo žinoma tik iš dabartines Afrikos tropiku˛ faunos. Palyginami skirtingu˛ autoriu˛ pateikiami akaliptratu˛ gausu-
.
mo paskaicˇiavimai tarp visu˛ vabzdžiu˛, dvisparniu˛ ir “tikru˛ju˛ musiu˛“ inkliuzu˛. Šioms musems priklauso mažiau negu vienas pro-
centas gintare randamu˛ inkliuzu˛. Šio retumo priežastys aptariamos kartu apžvelgiant retai pasitaikancˇias akaliptratu˛ sankaupas
. .
viename gintaro gabale. Ypatingos ir kartu unikalios morfologines apomorfijos, kuriomis pasižymi visos Žemes rutulyje sutinkamos
. .
akaliptratines muses, egzistavo jau terciare. Aptariami trys tokie pavyzdžiai. Diskusija apie abejotina˛ ta˛ pacˇia˛ vokiškojo Biterfel-
do ir Baltijos gintaru˛ kilme˛ išsprendžiama parodant, kad abiejuose gintaruose randama 15 vienodu˛ Acaliptratae ru–šiu˛. Vidinis
ru–šinis variavimas tarp gintaruose randamu˛ akaliptratu˛ ankscˇiau nebuvo tirtas. Remiantis 45 pavyzdžiais ir Protoscinella electrica Denisia 26,
. zugleich Kataloge der
(Chloropidae) holotipu demonstruojamas evoliuciniu˛ transformaciju˛ letumas kartu pagrindžiant 16 parinktu˛ požymiu˛ filogeneti- oberösterreichischen
ni˛ reikšminguma˛. Nušviecˇiamas polifiletinis sparno gyslotumo ir šeriuotumo redukcijos procesas, stebimas keliose akaliptratu˛ šei- Landesmuseen
Neue Serie 86(2009):
mose.
171–212
© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
Sistematikai skirtoje dalyje aptariama daug taksonomijai bu–dingu˛morfologiniu˛požymiu˛. Pridedamos dvi lentele.s, labai paleng-
vinancˇios kiekvieno rasto egzemplioriaus patikrinima˛ir dokumentavima˛bei padedancˇios suprasti klaidžias terminologijos ir trum-
piniu˛sistemas, naudotas dipterologijoje skirtingais periodais. Darbe pateikiami du skirtingi apibu–dinimo raktai: viename išvardi-
jami 97 išskirtiniai ar reti naujai pastebe.ti morfologiniai ypatumai, antrame bandoma apibu–dinti 56 aprašytas ir 161 rastas, bet
neaprašytas ru–šis. Vartojama gerai žinoma HENNIG‘o gintarui skirtu˛publikaciju˛serijos terminologija. Tai daroma norint paleng-
vinti šiu˛gana sude.tingu˛aprašymu˛ir gausiu˛iliustraciju˛bei dipterologine.s literatu–ros, išspausdintos iki 1981 m., kada buvo pasiu–
lyta nauja terminologija, analize˛. Visi ru–šiu˛perke.limai iš vienu˛šeimu˛ar gencˇiu˛i˛kitas, atlikti po HENNIG‘o laiku˛, išvardijami pa-
teikiant publikaciju˛nuorodas. Taip pat pateikiami ru–šiu˛“suskaldymai“, kurie i˛vyko ištyrus 1141 inkliuza˛.
Raktiniai žodžiai: apomorfijos, Biterfeldo gintaras, Calyptratae, Chloropidae, Pyrgotidae, ru–šiu˛susidarymas, variabilumas.
Introduction Material and methods
Since the opening of the Iron Curtain 20 years ago The optical observation of acalyptrate inclusions is
studies on amber insects underwent a new revival. a complicated procedure influenced by the amber ma-
Groups of amber friends were established, amber dealers trix itself and by the condition of their preservation. In-
learnt to identify the insect orders and families, and clusions embedded in transparent amber without impu-
they travelled around in order to present their stones to rities are quite rare, their morphological characters are
museums and private collectors. The authors of this ar- as easy to observe in such a piece as in extant fly speci-
ticle benefited from this boom and brought together a mens. In most cases, however, important structures can
special collection of Acalyptratae, a group of almost be obscured by crust of the amber surface, cracks, fis-
tiny flies, which were rarely selected from amber. Amber sures, gas bubbles, mineralic precipitations like pyrite,
acalyptrates had been identified in the past by some few plant debris or syn-inclusions. If an inclusion is situated
specialists only, most notably the world foremost au- directly beneath or nearby an opaque layer of resin it is
thority, Willi HENNIG. In a series of papers (1940, 1965, only visible from one side.
1966, 1967, 1969, 1971, 1972) he published compre-
A typical phenomenon of Baltic amber inclusions is
hensive and detailed research on the Baltic amber aca-
a milky coating (German term: Phloem, Verlumung) in-
lyptrates including a revision of MEUNIER‘s descriptions
around hundred years ago. For the determination of half terpreted often as “mould“ but caused by microscopic, liq-
a hundred species he really had to rack his brain. He uid-filled bubbles, almost only on one side of the insect
worked up the material of European and North Ameri- (presumably influenced by sun exposure during the em-
can collections in museums and palaeontological insti- bedding and following rotting process). This covering
tutes. HENNIGexamined 124 specimens, which he clas- can obscure the embedded objects partially or totally. In
sified in 30 families and 49 species out of which 39 were other cases the black insect bristles penetrate this coating
described as new. More than 300 printed pages offer us and are better visible than on shiny dark surfaces. Anoth-
a vast array of phylogenetic speculations accompanied er problem is a technical process used in the amber indus-
by excellent figures. HENNIGhimself spoke of situations try in order to clear opaque amber samples in a so-called
in which certain inclusions exasperated him. The read- “autoclave“. Amber inclusions, which were treated in a
er, not well understanding his complicated German*, high-temperature autoclave, are mostly more or less de-
may just as much been despaired in getting a clear pic- formed, compressed and dark-brown to almost black,
ture of his results. Surely that was one of the reasons looking “cooked“. The integument of the body is more or
that the subject was neglected after his death. less shrunk and bristles may have lost their connection to
the original point of insertion. Measurements of such fos-
Since HENNIG‘s last paper in 1973 just seven erratic
descriptions of Baltic amber acalyptrates were published sils are unreliable (see also SZWEDO& SONTAG2009).
though the flood of amber publications swelled up rap- The very first step before our analysis was processing
idly. Dirk TEUBER(Gütersloh), collector of amber liter- the amber pieces: cutting, grinding and polishing as
ature, altogether catalogued 3,306 books and articles for close and as parallel as possible to the frontal, dorsal and
the years 1550 till 2006. The increase of amber publica- lateral sides of the fly. Oblique views were occasionally
tions, step by step, over the last five decades since 1956 unavoidable if specimens were lying too close to the sur-
was as follows: 84, 104 (including 1976, the year of face of a round stone. Subsequent embedding in artifi-
HENNIG‘s death), 242, 729, and 1,233 (including 2006) cial resin, follwed by renewed grinding and polishing,
(pers. comm.), an impressive disproportion to the mere can eliminate a convex or concave surface of a stone, or
18 publications (cited below) since 1976 dealing at least it enables a perpendicular view on a wanted plain.
in a short part with some amber acalyptrates out of the
large number of families. * For an English translation see HENNIG1965.
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Moreover, such a procedure (always only after complete 1905 [new name for a homonymy by HENDEL 1923],
evaporation of all water in the fissures) protects fragile 1908, 1917). They were mostly stored in the former col-
samples from breaking and weathering. Two-component lection of the Königsberg University, East Prussia. After
polyester or epoxid resin, available in shops for craft World War II this collection was deposited at the “Ge-
supply, have a similar optical quality and refractivity as ologisch-Paläontologisches Institut der Universität
amber. Our labor-intensitive procedure facilitated the Göttingen“. According to HENNIG (1965) most types
stereoscopic investigation. All embedding should al- described by MEUNIERare safely stored. All modern in-
ways be done only after a first thorough study of an in- sights in the world of amber acalyptrates were presented
clusion in order to search for the most important struc- by HENNIG(1940, 1965, 1966, 1967, 1969, 1971, 1972,
tures for identification and correct grinding plains. 1973). In those times the Conopidae still were placed
Scientists need a lot of time to focus on an inclusion outside the Acalyptratae, today it is presumed that they
and to detect all characters necessary for a careful analy- would best be placed near the Tephritidae. STUKE (see
sis. If the main features, the chaetotaxy of head, thorax below) in his amber papers presents no opinion on this
and legs are impossible to observe because of obscured matter.
characters, bad position or an incomplete specimen, an
New genera and species were described as follows:
exact determination to genus or species, even to family
STUKE (2003, 2005) two new Conopidae; HOFFEINS &
level remains insufficient. But even such poorly pre-
RUNG (2005), one new Periscelididae; WOźNICA &
served flies often become valuable when further speci-
PALACZYK(2005) and WOźNICA(2006, 2007) altogeth-
mens of the same species are detected later on, as we
er three new Heleomyzidae; GRIMALDI(2008) one new
may use them for the study of singular additional details.
Camillidae. All these taxa are included in the identifi-
Altogether we investigated 1,141 individuals of aca- cation key below. Further studies, but without descrip-
lyptrates embedded in 1,063 stones, which (with the ex- tions of new taxa, were published by D.K. MCALPINE
ception of seven) had not been used in foregoing stud- (1966, Cypselosomatidae), MORGE(1967, Lonchaeidae
ies. Some are insufficiently considered in the identifica- and Pallopteridae), J.F. MCALPINE (1977, Proneottio-
tion key as they are loaned to other dipterists in Europe philidae), J.F. MCALPINE (1981a, Pallopteridae), J.F.
and abroad since several years. The material belongs to MCALPINE(1989, Clusiidae), SCHUMANN(1994, Diop-
the following collections: Museum of the Earth, sidae), WHEELER (1994, Carnidae), ROHÁCˇEK (1998,
Warszaw (1), Natural History Museum, London (1), Zo- 2006, Anthomyzidae), HAENNI (2003, collection), and
ological Museum, Copenhagen (1), EICHMANN (24), KOTRBA (2004, Diopsidae). EVENHUIS (1994) cata-
GRÖHN (57), HOFFEINS (465), KERNEGGER (86), LUD- logued all known fossil Diptera of the world including
WIG(13), TEUBER(2), VONTSCHIRNHAUS(491). compressions, impressions, trace fossils, copal, and am-
ber.
Results
Hermann LOEW and the acalyptrates
Historical background – the earliest and
The second scientist who detected acalyptrate flies
the present times
in amber was LOEW (1850). OSTEN SACKEN (1903-4,
A first description of four acalyptrate fly inclusions reprint 1978), in his classical book on his life in ento-
in Baltic amber was presented by PRESL (Prague) in mology, wrote 24 interesting pages on the character and
1822 (an extremely rare book present in only one pub- career of his colleague Hermann LOEWincluding also a
lic library of Germany, Göttingen). The types are as-
long chapter on his work on amber, which was never
sumed to be lost and none of the “Musca“-species can be
finished. Nevertheless, OSTENSACKENafter his long in-
allocated to a valid taxon (HENNIG1965). Before 1850 tercourse with LOEW “threw some light on this other-
LOEWbegan to study the dipteran inclusions of his pri- wise very obscure subject“. Also, in 1864, he made
vate collection and the large BERENDT-collection, LOEW‘s second amber article available in the English
which is housed at the “Paläontologisches Institut, Mu-
language, which was originally published in a journal
seum für Naturkunde“ at the Humboldt University of not easy to obtain today (LOEW 1861; OSTEN-SACKEN
Berlin since 1873. The LOEW-collection was purchased 1864). LOEWhimself wrote in a letter: “Minutiae are my
in 1922 by the British Museum of Natural History (now
true speciality, particularly when they fall within the do-
Natural History Museum) and is deposited in its Depart-
main of the Acalyptrata!“ His first sentences on amber
ment of Palaeontology. Three articles on amber acalyp-
Acalyptratae (l. c.) never were translated. As they were
trates were published by LOEW: 1850, 1861 and 1873. published in a nearly inaccessible “journal“, a school
Detailed descriptions of acalyptrate inclusions were programme of the gymnasium where he was the director,
made by MEUNIER in six articles (1895, 1899, 1904, we cite him here in our translation:
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“Fam. 21. Myopina. The Myopina contain only Ephydridae, a family with species not being abundant
one most curious species, which seems to require the de- within shady forests but mainly living along freshwater
scription of a new genus; it equals more a Myopathan a shores and marine beaches or developing on open
Conops, but it definitely misses the swollen head shape grassland as leaf-miners or snail-predators. (But several
of Myopa-species, moreover it has a quite short and species of Parydrinae were identified by specialists of
thick proboscis like that to be found also among extant ephydrids from Dominican amber; pers. comm.). Sure-
species of the genus Conops.“ It follows “Fam. 22. Mus- ly LOEW mixed up ephydrids with Periscelididae or
caria“ (see below) and “Fam. 23. [sic!] Anthomyina“ Aulacigastridae because of their similar fronto-orbital
(without any mentioned genus) continued by: bristles and partly convex and prominent face. One fur-
ther family, the snail-killing Sciomyzidae, was listed by
“Fam. 23. Acalyptera. I understand this family in
LOEW as doubtful. After our collecting activities this
that extent as MEIGENinterprets the Acalypteraein the
family 160 years later is very well represented with sev-
7thpart of his publication, but I exclude all those gen-
eral undescribed species. They are under study now by
era, which distinguish themselves by a variant habitus.
L. KNUTSON.
Out of the 28 species belonging here, only very few can
be determined up to genus level. Most of them belong In his 1861 article LOEWadded only one further un-
to the extremely doubtful objects. But I believe to have doubtful acalyptrate family, the Diopsidae, and he ex-
recognized with certainty the genera Sapromyza, pressed some ecological thoughts, exemplified by five
Helomyza, Ephydra, Drosophila and Chlorops. – These species of Diptera: “The following species may be named
and the two families mentioned above (Fam. 21. My- as indicative that the climate of the Amber period was
opina, Fam. 22. Muscaria) include a large and interest- very probably somewhat, although not very much,
ing part of the system: in spite of the richness of the ma- warmer than the present climate of Prussia: … 3.
terial, which passed my hands, I can contribute only Sphyracephala, a close relative of Sphyracephalabrevicor-
poor information. It may be explained by the fact that nis SAY, common in the middle and southern of the
among 200 amber flies hardly more than one can be United States, the only living representative of the
found, which belongs to the relationship of these three genus as yet known. …“ (translation by OSTENSACKEN
families. Collectors will render a special merit, if they 1864: 311). KOTRBA(2004) gathered all available 28 in-
pay attention to this group of related Diptera.“ clusions of Prosphyracephala succini (LOEW) and light-
ened diopsid evolution in her cladistic analyse of mor-
“Fam. 24. Leptopodea.I detected two nice Caloba-
phometric measurements. In addition LOEWadded some
ta-species, which belong to this family, which can be
further doubtful acalyptrates, mentioned here in the
distinguished so easily; the body size of one specimen
modern system: Lonchaeidae, Opomyzidae and Piophil-
equals that of the longest exotic species.“
idae. Last but not least, LOEW listed families which he
As“Fam. 22. Muscaria“ LOEW(1850) records 12-14 said he undoubtedly never saw in amber: (in the mod-
seen specimens of Calyptratae, families Muscidae, An- ern system) Psilidae, Ulidiidae, Tephritidae, Sepsidae,
thomyiidae, Sarcophagidae, and Tachinidae. He could Agromyzidae, Coelopidae, Asteiidae, and Sphaeroceri-
not order any of them to one of the three mentioned dae. Out of these, Psilidae have been separated by us re-
families, which to this day are all still unknown from peatedly, according to quantity followed by Pallopteri-
Baltic amber. Only one specimen of Anthomyiidae is dae. The families Sepsidae and Asteiidae still are ab-
known to date (MICHELSEN 2000). But one of us, solute rarities, while the marine Coelopidae from ma-
M.v.T., possesses one female of a poorly preserved ?Ta- rine shores (possibly LOEW‘s Phycodromidae were
chinidae with 9 larvae behind its ovipositor. Also H.-P. misidentified Dryomyzidae of which to date two fossil
TSCHORSNIG, specialist for this family, was not able to species are known) and Sphaeroceridae are unknown
confirm a reliable family identification. In Dominican inclusions until today with two exceptions: HELM
amber, too, these most “modern“ larger flies are ex- (1896: 223) mentioned two sphaerocerid specimens in
treme rarities, four species were only described to date his collection as “Borborus“, and one of us (M.v.T.) saw
(MICHELSEN1996; PONT& CARVALHO1997). Probably one Baltic amber specimen of this family with its pecu-
larger flies were powerful and quick enough to escape liar shortened hind metatarsi (= basitarsi) and the typi-
the sticky resin. Families which could be confirmed by cal thin long arista. Unfortunately, this inclusion seems
later authors had already been recorded by LOEW as to have been mislaid or stolen in the Bielefeld Univer-
“undoubtful“ inclusions in the following sequence sity, nevertheless we included it in the key but omitted
(modern taxonomy): Diopsidae, Conopidae, it from the other surveys. The absence of the last fami-
Heleomyzidae, Drosophilidae, Chloropidae, and Mi- ly remains an enigma as these flies are so abundant in
cropezidae. Though we studied much more material extant nature. But their ecology (occurrence in moist
than ever before we could not confirm any specimen of hidden rotting substrates and leaf litter) is not in coin-
174
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cidence with the abiotic conditions of sun exposed fresh vate hands were purchased from multi-pre-selected ma-
amber droplets on twigs and trunks. terial. Based on totally unselectedmaterial with special
reference to Diptera the following results were obtained
Further Eocene Acalyptratae by HOFFEINS & HOFFEINS (2003) after the selection of
39 specimens of acalyptrates:
Recently ZLOBIN(2007) studied types and other fos-
sil acalyptrates described by COCKERELL from the among 17,119 insect inclusions: 0.22%
“younger Lower Tertiary of the Hamshire basin (Bem- among 10,778 Diptera inclusions: 0.36%
bridge Marls. 35 m.y. B.P.)“, which had been ordered by among 2,125 Brachycera inclusions: 1.83%
EVENHUIS (1994) to the families Sphaeroceridae, among 1,351 Dolichopodidae inclusions: 2.88%
Richardiidae, Ephydridae and Chloropidae. They were
In a more general sense that means: in 2,000
recognized by ZLOBIN as Anthomyzidae, Ephydridae,
brachyceran inclusions less than 2% were acalyptrate
Chloropidae, Agromyzidae, Otitidae, Heleomyzidae,
Diptera and in about 1,350 inclusions selected as “fam-
and Lauxaniidae. One of us (M.v.T.) has studied the
ily Dolichopodidae“ (“long-legged flies“, the most com-
type of Protoscinis perparvus COCKERELL, 1917 in the mon dipteran family in amber) less than 3 were acalyp-
year 1994 and had identified and labelled it as an ephy-
trates. In the words of our experienced friend A. KRYLOV
drid, tribe Scatellini. The transfer was officially pub-
(Kaliningrad): among 1,000,000 unselected grinded
lished now after ZLOBINcame to the same result, remov- stones “fresh“ from the deposit, onlyoneacalyptrate in-
ing this taxon from the Chloropidae. Some dipterists are
clusion may be picked out, out of all scientific useful in-
not content with some of the further transfers. They are
clusions 0.04%, while out of all Brachycera 0.5% are
mentioned here as European Tertiary acalyptrates for
Acalyptratae, 0.5% Syrphidae and Pipunculidae, and
the sake of completeness. In the same context one out
2% are Rhagionidae, Tabanidae and Asilidae.
of eleven articles on fossil mines of the larvae of
leafminer flies (Agromyzidae) in trunks of Tertiary trees SONTAG(2003) selected from 3,875 checked stones
1,824 pieces containing zoo-inclusions: 4 acalyptrate
(SÜSS 1980) is cited here in order to demonstrate that
flies, all ?drosophilids, were obtained only:
our search for a possible worldwide first confirmed am-
ber agromyzid did not reveal any adult fly. It is not un- among 7,111 animal inclusions: 0.0006%
derstandable that just the only cambium/xylem miners among 4,933 insect inclusions: 0.0008%
among the order Diptera are absent in amber though to- among 2,947 Diptera inclusions: 0.0014%
day they are abundant in tropical forests (VONTSCHIRN- among 402 Brachycera inclusions: 0.9950%
HAUS 1991) and are as well occurring everywhere in SONTAG (2004) identified all 6,096 Diptera inclu-
northern temperate latitudes. Oak trees (Quercus spp.)
sions in the Gdansk Amber Museum to the family lev-
are hosts of Phytobia mallochi(HENDEL, 1924) in Europe el, which are 50% of all arthropods and 65% of all in-
(VONTSCHIRNHAUS1993: 480). But timber of the abun- sects in the museum. Only 8 acalyptrates were detected:
dant oak trees in Baltic amber forests – stellate hairs of
6 Drosophilidae, 1 Psilidae, and 1 Micropezidae, alto-
their flower buds are to be found in nearly each amber
gether 0.013% of all Diptera.
piece – seems not to have been attacked by Phytobia-
flies or their ancestors. This short overview demonstrates the influence of
different sampling and selecting methods. The differ-
ences of counting on the basis of all Diptera between
How many inclusion stones must be
collected to find one member of HOFFEINS & HOFFEINS and SONTAG are 0.36% and
0.001%, respectively, that means the first authors de-
Acalyptratae?
tected 265 times more acalyptrates among all Diptera
LOEW’s (1850) rough estimation of the percentage than their Polish colleague! LOEW, HOFFEINS & HOF-
of acalyptrates among all his identified flies, being one FEINS, andSONTAGcounted0.5%, 1.8% and 1.0% aca-
out of 200 (0.5%) (“… das[s] auf 200 Bernsteinfliegen lyptrates, respectively, among all identified flies
schwerlich mehr als eine kommen wird“), suits the fol- (Brachycera), an astonishingly similar result, which let
lowing compilation well: Three labour-intensive inves- us speculate that mainly the thorough counting of all
tigations on the abundance of Diptera have been pub- Nematocera (midges and gnats) among the Diptera in-
lished, which contain records on Acalyptratae (HOF- fluenced the sums and percentages.
FEINS& HOFFEINS2003; SONTAG2003, 2004). Rareness
is the common result. Geological duration
Any statement concerning a frequency expressed as of the amber forests
percentage seems more or less speculative because all in- We are not specialists for the question when the
clusion collections in institutions as well as most in pri- Baltic amber forests emerged and when they decreased.
175
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We need this information for the next chapters, thus let too. They provoke the question when in the dark past
us cite Wolfgang WEITSCHAT(2008: 94) in our transla- such peculiarities evolved and which were their provok-
tion of an article not easy to obtain for entomologists ing adaptations. Another example is the Clusiidae with
outside of Germany: their specific 2ndantennal segment bearing a triangular
extension at outer surface lapping over onto the 3rdar-
“The genesis of amber in northern Europe probably
ticle. We cannot present any speculation about possible
started already during the climatic optimum in the Low-
benefits of such a phylogenetically stabile minute mor-
er Eocene and possibly was already finished towards the
phological detail.
end of the Middle Eocene. As meanwhile confirmed the
definite cooling of Northern Europe during the transi- Last but not least, we point out a third interesting
tion time Eocene/Oligocene caused an irreversible example out of so many others: the first two species of
floristic change from palaeotropical towards arcto-Terti- fossil Pyrgotidae, which we detected in amber, of which
ary elements. A similar destiny might have affected fau- one already possesses only one ocellus. Extant Pyrgoti-
na and flora of the ‘amber forests’. This assumption is dae predominantly are dawn- or night-active tropical
supported by the identity of organisms concerning the parasitoids of big scarabaeid beetles. Already in the Ter-
species-level of both deposits, especially of the tropical- tiary or earlier they had reduced two of the three
faunistic and -floristic elements. This fact is now defi- ground-pattern ocelli, a process which seems still pro-
nitely documented by analysing the spider fauna. Baltic gressing. Extant forms predominantly reduced all ocelli
and Bitterfeld amber originate from one single ‘amber but some still possess one or three or rudimentary ones.
forest’ in western Scandinavia, which ranged over a pe- At least one of our species has very peculiar claws, not
riod of up to 10 million years during a balanced subtrop- curved normally but bent over in an abrupt angle of 90°,
ical-tropical climate …“ never seen in other flies. These specialized claws seem
to have been an adaptation to grasp glossy surfaces of
Diversity and Apomorphy beetles during nocturnal flight (as stated for extant
A recent updated counting of the diversity of Aca- species) for oviposition into their abdomen. They were
lyptratae in Germany (VON TSCHIRNHAUS 2008) re- already developed 45 million years ago! Similar to most
vealed 1,927 published species belonging to 51 families. recent species it is a large acalyptrate in adaptation to
Agromyzidae (leaf miner flies) were counted by 552 the large size of its presumed hosts. Extant pyrgotids pre-
species, not including 102 additional undescribed dominantly feature a singular character among the
species from Germany in the VONTSCHIRNHAUS-collec- higher Diptera, the absence of a “mid-coxal prong“, a
tion; some 170 valid further species are known from our soft but complicated structure above the mid-coxa of all
directly adjoining neighbouring countries, altogether other higher Diptera. We cite only one of several papers
we await 724 species. The second place in extant diver- of the same authors dealing with the biomechanics of
sity holds the Chloropidae, 198 published German this structure: FRANTSEVICH& FRANTSEVICH(1999). In
species, followed by 177 Ephydridae, 137 Sphaeroceri- opposition to the statement in several manuals or hand-
dae, and 110 Tephritidae. Among these only the books of Diptera, one of us (M.v.T.) saw one Nearctic
chloropids are regularly present in Baltic amber, Proto- (Pyrgota undataWIEDEMANN) and some extant tropical
scinella electrica, and two rare species, Protoscinellasp.n. pyrgotids still possessing the prong. One of our fossil
and Tricimbasp.n.; P. electricais one of the most abun- species is so well embedded that we can document that
dant acalyptrate fly species in Baltic amber though only the loss of the prong in some of the species of the pyr-
the holotype was known hitherto. (We can also state, gotid family was already finished in the Tertiary. Anoth-
that Tricimba-species belong to the dominant acalyp- er peculiar morphological detail in some extant pyr-
trates in Dominican amber, which are all still unde- gotids is “hind tibia sometimes with basal third rather
scribed). Three specimens of Sphaeroceridae are men- suddenly smaller in diameter than apical part (Fig. 6)“
tioned in the chapter on H. LOEW. (STEYSKAL1987). Just this can be observed in our fossil
species. But different than the extant species the fossils
The three chloropid species possess all family-specif-
still bear a dorsal preapical bristle (dpr), belonging to
ic apomorphic characters also known from extant
the groundpattern of acalyptrates, at least on the hind
Chloropidae including two apomorphic features singu-
tibia. The presence of these setae demonstrates that
lar among all Diptera: a sharp perpendicular ridge along
there was an ongoing evolutionary rudimentation
the propleuron and a small kink or flexure in the basal
process since the Tertiary.
part of the m -vein which marks the junction point of
3+4
a crossvein lost at least during the Cretaceous times or
earlier. Such specific apomorphisms (“modern“ charac-
teristics) can be documented for most other families,
176
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Intraspecific variation within millions of lae along the hind edge of the eye down to the height of
the lower point of the figured 3rd antennal article, (2)
years exemplified by Protoscinella
hairs on the front side of the 1stcoxa, (3) hairs on the
electrica (Chloropidae)
lower side of the stem of the proboscis, (4) a well ob-
One example of morphological variability should be
servable pubescence around the 3rd antennal article
demonstrated: Producing our provisional key for the
which is equal in its length to the diameter of the basal
identification of fossil acalyptrates embedded in resin
diameter of the arista and (5) three moderately im-
over a period of estimated 10 million years (WEITSCHAT pressed longitudinal grooves along the central mesono-
2008) we came across the problem where the limits of a
tum (Fig. 19 in the present article), a peculiar character
species definition should be drawn. It is well known that
among amber acalyptrates, shared only with Protoscinel-
the velocity of speciation and morphological modifica-
la sp.n. and Tricimba sp.n. (as well the extant further
tions is different in different animal groups. Extant
genera Aprometopis BECKER, Pseudotricimba ISMAY and
species of millipedes (Diplopoda: PolyxenusLATREILLE,
Tricimbomyia CHERIAN). These grooves are accompa-
1803, worldwide distribution) or exceptional spiders
nied or “filled“ by a “criss-cross“ arrangement of acros-
(Araneae: Archaeidae KOCH& BERENDT, 1854 with the
tichal micro-setulae, just as in the genus Tricimba, ex-
fossil genus Archaea L., 1758 and three similar extant
tant, or fossil, inclusive checked undescribed species
genera in Madagascar, South Africa and Australia)
from Dominican amber. The newly detected inclusions
among the land living arthropods look quite equal to
revealed two highly interesting features important in
their fossil relatives preserved in Baltic amber. Their life
systematics of Acalyptratae: All world members of the
strategies and ecological niches seem to have remained
family Chloropidae can be identified to the family level
stable. In Polyxenusthe predominantly parthenogenetic
by a sharp dorso-ventrally running ridge at the fore-edge
mode of reproduction in extant representatives may be
of the propleuron (anterodorsally of the first coxa), at
presumed for the Tertiary only if more specimens (than
first used in a family key by MALLOCH (1948). As this
we saw) turn out to be females. In palaeontology we can
line is situated very near to the back of head its detec-
rarely find an object in which evolving minute struc-
tion in side-view is not easy. The second peculiar fami-
tures, such as single bristles, can be studied as if the
ly-specific structure is a slight flexure or kink in the
specimens were collected today. The variability within
basal part of the 6thlongitudinal wing vein reaching the
the evolving process of Protoscinella electrica(Chloropi-
costa, namely m (= M , = CuA), which marks the
dae, Oscinellinae) over a period of millions of years can 3+4 3+4
very point where two lost veins belonging to the
be compared with the interspecific variation of the sis-
ground-pattern of flies, the “basal-medial cubital cross-
ter genus TricimbaLIOY, 1864differing only morpholog-
vein“ tb (= bM-Cu) and the “anal cross-vein“ (= CuA )
ically in the absence of setulae on the dorsal side of the 2
coalesced with the longitudinal vein m (abbrevia-
subcosta vein. ISMAY (1993) published an impressive 3+4
tions outside round brackets used here in accordance
overview on the interspecific morphological variety of
with the discussed monograph of HENNIG[1965], those
this genus in the zoogeographical region of Australasia,
inside parenthesis after MERZ& HAENNI[2000]).
which is an example also for the Tricimba-species in oth-
er world regions including Europe. Compared with the The following selected 16 characters (in our proto-
succeeding extensive splitting in chloropid systematics cols noted for each specimen) are subject of interesting
ISMAY’s concept of the judgement of morphological de- transformations, which are judged here after a dash as
tails (judged as not being important enough for a split- plesiomorphic (ancient), apomorphic (progressive) or
ting of this genus) is welcome. as a questionable condition.
Altogether 45 inclusions (subsequently called “se- (1) In the description of the holotype short but dis-
ries“) of P. electrica could be studied, including the Y- tinct ocellar bristles (oc) are figured, divergent and bent
holotype from the Copenhagen Museum, 1= from the backwards (an important direction in world chloropid
London Natural History Museum, 3== from the taxonomy, partly used in keys for the genus level). The
GRÖHN-collection, and 2YY from the KERNEGGER-col- ocellar tubercle, situated within a larger bare ocellar tri-
lection. Never before so many specimens of one fossil angle, not figured by HENNIG, is covered by tiny irregu-
species of acalyptrates could be analysed. It is not easy lar setulae, too weakly figured in HENNIG‘s description.
to decide if only one or several species or subspecies are These setulae are always present. The ocellars, normal-
present among this series though one of us is familiar ly stronger than the setulae, never are longer than in
with the variability of extant chloropid species includ- HENNIG‘s figure, often they are shorter, partly they are
ing Tricimba-species. HENNIG (1965) in his description parallel and not divergent, partly they are upright and
of the badly preserved holotype added good figures, not pointing backwards, partly they are not differentiat-
which only omitted (1) the continuation of the spinu- ed in thickness or length from the surrounding setulae,
177
© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
in such a case to be judged as “absent“. — Backwards or bristle has been reported to be absent. But LAMB(1918:
absent: apomorphic. 391-2) describes just this bristle from Cestoplectus
(2) The distinct pubescence of the always dark 3rd intuensLAMB, 1918 (Botanobiini), and CHERIAN(1989)
from the strange looking Tricimbomyia muzhiyarensis
antennal segment (not figured by HENNIG, see 2ndpara-
graph above) ventrally of the basis of the arista is bent CHERIAN, 1989 (Tricimbini), both belonging to the Os-
forwards for a short distance, than abruptly it is contin- cinellinae subfamily in modern taxonomy. BECKER
(1911: 39) described a supraalar bristle and two noto-
ued without space but bent upwards. The transforma-
pleurals in his new genus Ochtherisoma from Australia,
tion series includes both, short and long pubescence,
the latter being the exception in extant Chloropidae. In later sunk as a younger synonym of Aragara WALKER,
living chloropid species such a difference in the length 1860. Emilia NARTSHUK was so kind and checked this
genus from the St. Petersburg collection: “I cannot see a
of the pubescence could be used for species definitions,
supraalar, only 1+2 notopleural setae“. The fewest world
we know such a case in an otherwise inseparable Euro-
genera have been investigated in this context, and dis-
pean new Conioscinella-species reared by M.v.T. from
covery of an ia in other oscinelline genera can be await-
cones of Norway spruce. — Long: apomorphic, compare
ed. In our series in principle such a group of bristles is
figures of Tricimbaspp. in ISMAY(1993), especially that
present, sometimes including more, sometimes fewer se-
for T. antennataISMAY.
tae, mostly one or two or three longer and 0-4 smaller
(3) HENNIG figured 20 mico-setulae on the upper ones. Synchronously embedded specimens (see Table 1)
side of the wing vein “radius 1“ (r ), an important char-
1 possess different sets of ia, which verifies the variation
acter for taxonomy of Acalyptratae and singular in
at the same time segment. But one single bristle, the
Chloropidae, occurring only in the fossil genus Proto-
ground pattern in acalyptrates, rarely occurs in Proto-
scinella. (Rows of hairs in another combination on the
scinella. Such a condition is found in our Tricimbasp.n.
lower and upper side of the veins r and r , respec-
2+3 4+5 with its extremely similar habitus. — More than one
tively, are present in Cestoplectus intuens LAMBfrom Sri bristle: apomorphic in the light of size-reduction of bris-
Lanka (LAMB 1918: 391-2). HENNIG‘s figure cannot be tles in the chloropid family.
confirmed for the holotype because the specimen now is
embedded in Canada balsam, the setulae are not count- (5) The scutellum of the holotype, flat above as in
able any more. In our series no specimen was found with all further specimens, bears three lateral bristles (la)
so many setulae. As these setulae are pointing distally in near the apical pair of scutellars. The whole scutellum is
the very direction of the vein fundamentally they are rugose (coarse, tiny pits each equipped with a micro-se-
very difficult to detect against their dark background, tula). Such an appearance makes it difficult to decide if
counting needs observation in extreme profile at a mag- in a lateral position thicker and prolongate setae are
nification of at least eightyfold. Intensive cold-light il- present. As in extant and our fossil Tricimba-species the
lumination must be used from all directions. The basal lateral side of the scutellum tends to become perpendi-
socket of each setula can be seen rarely as a light or a cular and it is as well equipped with the rugosity. Our se-
dark point against the surrounding resin. The number of ries shows all conditions, apical scutellars alone, thin
setulae partly is different in the right and left wing. Vari- and short, or slightly thickened and elongate lateral
ation includes 1 till 12 setulae, also the length of the se- ones, surely not homologous with the true lateral bris-
tulae varies. The following numbers were counted tles in dorsolateral or lateral position of the basal half of
checking 57 visible wings (number of setulae/ number of the scutellum of other acalyptrates. — Some few cumu-
wings) 1/1, 2/4, 3/4, 4/2, 5/7, 6/8, 7/6, 8/9, 9/6, 10/6, lative extended lateral bristles near the apicals: apomor-
11/2, 12/2. The detection of one single similar setula on phic.
the distal end of both r -veins of an undescribed Astei-
1 (6) In the chapter “Diversity and Apomorphy“ the
idae (see couplet 25a of the key), which is bent side-
peculiar curvature of vein m was mentioned. HENNIG
wards and distally, is highly interesting. — Few setulae: 3+4
indicated this kink in his fig. 316 by a tiny notch. In
apomorphic.
some exceptional extant chloropids among more than
(4) A peculiar group of four short upright bristles in 2,000 valid species this curvature, expression of the phy-
the supra-alar position is figured by HENNIG (l.c.), two logenetic background, disappeared. MALLOCH (1940:
longer and two shorter ones. In profile they can be dis- 261) mentioned the genera Siphunculina RONDANI,
tinguished from the more close-fitting mesonotal bris- 1856, Tricimba LIOY, 1864 (under its synonym Euhip-
tles, which follow centrally and backwards. From none pelates MALLOCH, 1925), and Platyina MALLOCH, 1927.
extant chloropid-genus such a group is known, species Among others it can be observed in the abundant Euro-
belonging to the plesiomorphic Siphonellopsinae pos- pean Elachiptera cornuta (FALLÉN, 1820). Our series
sess only one single sa-bristle, in other chloropids this shows that the process of downsizing of the anal cell (=
178
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CuA ) was still in progress during the Eocene. Different depths of the grooves. — Deep grooves: apomorphic.
2
from all extant chloropids in several inclusions a small
(9) Prolonged probosci evolved in several genera of
and narrow nearly closed anal cell (= cup, posterior cu-
Chloropidae, as well in Oscinellinae as in Chloropinae.
bital cell of modern manuals) is developed, in others the
During this process mostly the number of pseudotra-
apical closing cross-vein is only noticeable as a weak
cheae of the labellum (distal soft symmetric part of the
fold, a contradiction to the definition of modern
proboscis) was remarkably reduced. Like in the acalyp-
Chloropidae in all handbooks. Even a faint remnant of
trate fly family Milichiidae, the sister family of Chlorop-
the tb-crossvein (= bM-Cu, separating dm and bm cells
idae, several extant kleptoparasitic chloropid species
after modern terminology) is visible in several speci-
can be observed participating in the meal of spiders, dip-
mens. It is not joining the m (= M) in a more or less
1+2 ping their mouth parts in the pre-digested prey. One in-
right angle but in front of it it curves proximad (direc-
teresting example from Greece reported by HARKNESS&
tion to the wing base) “demonstrating“ its ancestry from
ISMAY(1976) may be cited here. Such a behaviour could
a longitudinal vein. A dispute about the phylogenetic
be suspected also for P. electricain the past because of its
background of the ground pattern “flexure of the m
3+4 long proboscis, which in optimal preserved specimens
vein“ is solved now on the basis of our fossil species.
exhibit a bifurcated acute tip and only 2 or 3 pseudotra-
With the distal end of this vein, equal with the notch in
cheae each side, quite a low number compared with
HENNIG‘s fig. 319, the rudiment of the anal cross-vein is
“normal“ extant chloropids. No transformation series is
joined, too. Last not least no remnants at all are de-
detectable; the length of the proboscis remained stable
tectable of two veins, the anal vein, a (= A + CuA )
1 1 2 through millions of years! In contrast to that we observe
and the axillaris, a (= A , posterior branch of the anal
2 2 a high intraspecific variability within the abundant Eu-
vein). It is of high interest that already in Eocene all
ropean Oscinimorpha minutissima (STROBL, 1900) and
these rudiments were finished or highly advanced. — A
three European Trachysiphonella-species concerning the
fragmentary not fully closed anal cell and a tb (= bm-
length of their extended probosci (T. poriHARKNESS&
cu) both faintly present: plesiomorphic.
ISMAY, 1976 has an exceptional long proboscis as veri-
(7) Chloropidae do not possess a complete subcosta, fied by M.v.T. in new Greek material from Lake Kerki-
in several extant genera worldwide this vein is hardly ni). — Long proboscis: apomorphic.
detectable as a short basal fold even missing its faded
(10) In extant chloropids long probosci are mostly
distal part. In the series of P. electricapartly an obvious
accompanied by extended palpi, an example is again the
developed fold can be observed ending farer proximal of
species O. minutissimamentioned above and in addition
r than indicated in HENNIG‘s fig. 319. A subcostal
1 Siphonella oscinina(FALLÉN, 1820), developing in spider
break is narrow, not indented and not accompanied by
cocoons. The palpi of P. electrica underlie certain vari-
special setulae on the costa, sometimes very difficult to
ability from normal and robust till slender and long,
detect. Some few extant chloropids like species in the
from yellowish till dark. — Long thin palpi: apomor-
genus PemphigonotusLAMB, 1917 miss this break, which
phic.
is possibly a plesiomorphy. — A throughout its length
visible weak sc and a tiny costal break: both plesiomor- (11) Prescutellar bristles (prsc) in Oscinellinae, to
phic. which Protoscinellabelongs, are often difficult to detect
as they are standing very near to the suture between
(8) The mesonotum (= scutum) of some few extant
mesonotum and scutellum and often are scarcely longer
Oscinellinae may possess 2, 3 or 5 moderate or deep
than the acrostichals adjoining in front. Distinction
grooves, partly accompanied by rugosity and criss-cross
may be possible by their slightly more robust appear-
arrangement of accompanying microchaetae in all
ance. In amber specimens their counting turns out to be
transformation conditions. Weak expression for exam-
difficult as well from dorsal as from oblique lateral. The
ple is present in several species of the genera Co-
holotype clearly has well developed prsc but our series
nioscinella DUDA, 1929, Aphanotrigonum NARTSHUK,
shows all conditions: prsc absent, each side 1 slightly
1964 and Oscinimorpha LIOY, 1864, strong expression in
elongate or short, 2 short, 3 short ones in one transverse
Tricimba LIOY, 1864, Aprometopis BECKER, 1910 and
row, both sides together 10 bristles including the inner
Tricimimyia CHERIAN, 1989. The last genus can be or-
postalars (ipa) and dorsocentrals (dc). The outer posta-
dered in the nearest relation to Tricimbaand Protoscinel-
lars (epa) are distant and do not appear as members of
la, the presence of the sa-bristle in all three has its com-
this “row“ — One prsc plesiomorphic; 0, 2 and 3 prsc
mon phylogenetic background. If the sa- and r -bristles
1 apomorphic.
are overlooked in these small flies, they would be iden-
tified as typical members of the genus Tricimba. The dif- (12) In P. electricathe ipa insert exceptionally near
ferent specimens of our series exhibit slightly different to the scutellum compared with extant Oscinellinae.
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Table 1:Collocation of aggregated acalyptrates in one piece of amber. Each (14) Eyes of P. electricaare mostly covered by dense
comma separates one stone. long pubescence confirmed also for the holotype. Some
Family Species ==:YY specimens only possess dense short pubescence, in some
Camillidae Protocamillasp. 2:3, 2:0, 1:2, others these fine microchaetae cannot be detected.
Campichoetidae Pareuthychaeta electrica 2:6, 1:1 Both conditions occur in extant species of the sister
Campichoetidae Pareuthychaeta minuta 1:2, 2:0 genusTricimba. — Judgement uncertain.
Campichoetidae Pareuthychaetasp. 2:2
(15) Cerci (posterior appendages in the male epan-
Chloropidae Protoscinella electrica 2:1 + 1 Acroceridae, 2:0, 2:0,
2:0, 2:0, 0:2 drium) were not described by HENNIGas the sex of the
holotype could not be ascertained by him. One of us
Chyromyidae Gephyromyiella electrica 1:2
Cypselosomatidae Cypselosomatites succini 1:1 in copula (M.v.T.) identified it as a female. All our males, 50% of
familia inc.sed. gen.sp. 6 all specimens, possess large-scaled rounded cerci with
Heleomyzidae Protoorbellia hoffeinsorum 2:0 long hairs around their edge. Their outline, well to be
Heleomyzidae Suillia major 0:1 + 0:1 Camillidae + 1:0 inc. seen in lateral view, shows slight variation towards a
sed. more acute lower posterior end in some few specimens.
Heleomyzidae ? gen.sp. 0:4 — Not evenly rounded: apomorphic.
Megamerinidae Palaeotanypeza spinosa 0:1 + 0:1 Palaeotimia lhoesti,
Dryomyzidae (16) The length of body and wing of each specimen
Micropezidae Electrobata tertiaria 0:3 (24==, 21YY) was measured. With one exception the
Milichiidae gen.sp. 1:3, 4:0 ratings show a Gaussian distribution: Body (without
Proneottiophilidae Proneottiophilum extinctum 0:4 + 2 + 1:0 + 1:0 ovipositor and antennae): 1.52-2.52 mm, on average
Heleomyzidae (coupl. 89b)
2.06 mm; wing 1.35-2.03 mm, on average 1.70 mm. One
Psilidae Electrochyliza succini 2:0
well preserved female with identical morphology is
Sciomyzidae gen.sp. 2:1
placed far outside these ranges: body 3.11 mm, wing
2.40 mm. — The normality in 44 specimens supports
Table 2:Species of acalyptrates identified from both deposits, Baltic and
that only one species is involved. Extreme sizes, short or
Bitterfeld.
long, are not connected with plesiomorphic or apomor-
Anthomyzidae Protanthomyza collarti phic conditions of other characters.
Camillidae Protocamilla succini
Palaeontologists working with marine or freshwater
Campichoetidae Pareuthychaeta electrica
Chloropidae Protoscinella electrica organisms and their rich material of transformation se-
Cryptochaetidae Phanerochaetum tuxeni ries from much longer lasting geological periods will not
Diopsidae Prosphyracephala succini understand our enthusiasm. But terrestrial animals nor-
Drosophilidae Electrophortica succini mally underlie quicker changes of climate conditions
Heleomyzidae Electroleria alacris and other unbuffered catastrophic events. Their fossil
Heleomyzidae Suillia major record is always extremely poor. For a dipterist confront-
Heleomyzidae “Heteromyza”dubia ed with the tremendous difficulties in species separation
Milichiidae Phyllomyza jaegeri of our present fauna P. electricais an impressive example
Pallopteridae Pallopterites electrica for the slow evolutionary process of altering minute
Proneottiophilidae Proneottiophilum extinctum characters all appearing to be independent from one an-
Pseudopomyzidae Eopseudopomyza kuehnei other. Finally the discussed transformation series ended
Psilidae Electrochyliza succini
in at least one further Protoscinella-species (with much
smaller 3rd antennal segment, different cerci and other
Thus they may be overlooked or allocated wrongly. In
reductions) and the first detected fossil Tricimba-species
the figure of HENNIGthey were omitted. The holotype is (with all characters of extant Tricimba-species, except a
embedded in lateral position, became blackish and is present sa-bristle of the fossil) both included in our key.
enfolded in iridescent fissures, the prsc are masked. In Hundreds of extant Tricimba-species are distributed
the series they rarely are absent but, if present, they al- worldwide, which in a large extend are still undescribed.
ways insert adjacent to the edge of scutellum. — Ab- The never-ending discussion about whether genera of
sent: apomorphic. the Tertiary age are surviving to date can be answered
without hesitation: Yes! Protoscinellaand the mentioned
(13) Fig. 314 in HENNIG‘s monograph (l.c.) shows a millipede and spider genera from Baltic amber are best
small setula between the vertical bristles vte and vti,
examples.
rarely to be observed in acalyptrates. In our series this
setula mostly inserts in the same position, rarely outside
of the vte. — Position without judgement.
180